• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

Card Range To Study



Play button


Play button




Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

37 Cards in this Set

  • Front
  • Back
  • 3rd side (hint)

Definition of refrigeration

The science of producing and maintaining a temperature below that of the surrounding area

State the reasons why refrigeration machinery is used in the RNZN

Preserve food supplies

Provide air conditioning

Provide chilled water cooling to electronic cabinets

Making ice for domestic use and medical purposes


What are the advantages of freezing foods?

Frozen foods are readily prepared, saving time and labor

Easier portion control and labor

Compact storage

Foods are always in season

Additional stocks in hand

Guaranteed quality


3 types of heat transfer, give an example of each

Conduction- heat transmission by contact. Eg through a steel bar

Convection- the natural movement of heat within a liquid or gas

Radiation- the transfur of heat by electro magnetic waves

Maximum fill of a recovery cylinder?


What are the laws of refrigeration

1. A liquid can be made to evaporate, or boil, either by adding heat or reducing the pressure on the surface, or a combination of both

2. A vapour can be made to liquefy, or condense, by increasing the pressure acting upon it, by extracting heat, or by a combination of both.

3. Heat travels only from an area of high concentration to one of low concentration (heat will flow from warm to less warm)

4. An evaporating liquid that is cooler than its surroundings will accept from its surroundings, yet remains at the lower temperature until evaporation.

Draw and label heat graph diagram

What is an oil separator and how does it work?

The separator is made of a welded steel cylinder with a fine wire mesh internal arrangement. The gas changes direction passing through the mesh throughing tiny oil particles out by using centrifugal force. The pil drops to the bottom and accumulates until it lifts the float valve removing the oil back to the compressor.

Name the safety devices fitted to the refrigeration plant

High pressure cut out

Low pressure cut out

Combined low and high pressure cut out

Where will you find the safety procedures for refrigeration

NZBR 2020


Are there any other references in other BRs for refrigeration


As for sentry posted outside the refrigeration compartment what would initial response be to a casualty?

Raise the alarm gas gas gas

Give the location of the incident to HQ1

Don BA and enter compartment place eeda on all casualties.

Under no circumstances enter compartment without BA

Assits duty watch/standing sea emergency party with casualtie evacuation

As a result of the ozone layer protection act 1990 the RNZN has converted most refrigeration machinery to what refrigerant, and why?

Most machinery is run on R134A or R404A as they have zero ozone depleting properties and are environmentally friendly not like the older R12 and R22

Why are safety devices fitted to refrigeration systems?

To minimize danger to personal, damage to machinery, and loss of expensive refrigerants.

What is the effect on the boiling point of a liquid if:

Lower pressure acting on its surface?

Increase the pressure acting on its surface?

Boiling point is reduced and less heat it needed

Will increase the boiling point, more heat is required to make it boil

Complete the following sentence

Refrigerant 134a & 404a have__________hence is more__________

Zero ozone depleting propertie potential

Friendly to the environment

If there was any moister in the refrigerant what problems would it cause?

Would cause water to freeze in the oriface of the expansion valve, thus blocking the valve and stopping the flow of refrigerant to the evaporator.

What are the potential health effects of refrigerants and explain them?

Eyes- liquid refrigerant in the eyes may cause blindness by freezing the moisture in the eyes.

Skin contact- liquid refrigerant coming in contact with the skin may cause serious frostbite

Suffocation- refrigerants are heavier than air and will readily replace the air in a space or lungs

Electrical shock- extreme care should be taken while working on any electrical component

Name the main and subtypes or refrigerant compressor used in the RNZN

Reciprocating compressor

Open type compressor

Semi-hermetic compressor

Domestic hermetic compressor

Screw compressor


Draw and describe how the thermostatic expansion valve works

Evaporator outlet pipe has a sensing Phil which reacts to temperature change. If the evaporator outlet temp is high the gas in Phial heats up and expands. This increases pressure in the valve which pushes down the push pin opening the valve, allowing more refrigeration to flow into the evaporator and allowing more heat to be removed. Valve closes when temperature drops and Phial gas contracts.

Explain the common refrigeration terms

Latent heat


Dew point


Hermetically sealed unit

Sensible heat

Sub cooling


Absolute pressure

Change of state

Latent heat- heat added or removed which cannot be measured by a change in temperature but accomplished by a change in state

Charge- amount of refrigerant in a system

Dew point- the temperature at which moisture in the air will condense if cooled at constant pressure

Cycle- complete course of operation of refrigerant back to the start point.

Hermetically sealed unit- a sealed unit in which the compressor and compressor motor are enclosed in the same housing with no external shaft or shaft seal, and the compressor motor operates in the refrigerant atmosphere.

Sensible heat- heat added or removed which can be measured by a change in temperature of the fluid or substance.

Sub cooling- process of cooling liquid refrigerant below condensing temperature, for a given pressure.

Superheat- is the additional heat absorbed by the gas, thereby increasing its temperature without further changing its state.

Absolute pressure- absolute pressure is measured from absolute zero rather than atmosphere pressure. It equals gauge pressure minus 14.7 psi or 100 kPa Change of state- change from on phase, such as solid, liquid or gas


Change of state- change from on phase, such as solid, liquid or gas

What are the arrangements for ventilation of refrigeration compartments

All compartments containing refrigerant machinery should be ventilated with a natural supply of air and the exhaust kept running at all times when machinery is running or being maintained

What safety precautions should be under taken in regards to the ventilation before entering a refrigeration compartment?

Before entering any compartment contening refrigerant machinery, the ventilation to and from the compartment is to be inspected to ensure that the ventilation fans are running and the flow of air is unrestricted.

What is the best treatment for overexposure to refrigerants

Get the victim to air

Can you smell refrigerant


Overexposure of refrigerations can cause

High concentrations can cause

Very high concentrations can cause

High concentrations cause feelings of light headedness and dizziness

Very high concentrations cause unconsciousness and death and an irregular heartbeat, which can be fatel

The ozone layer protection act 1990 stipulates what?

That it is illegal in New Zealand go knowingly or without lawful justification or excuse, release a controlled substance into the atmosphere while installing, operating servicing, modifying or dismantling any refrigeration or AC equipment or other heat transfer medium.

What is the NZDF policy when working on refrigeration type equipment?

states that equipment susceptible to leakage of uncontrolled substances is to be carried out strictly IAW existing and improved servicing instructions

What is the fail mode of the thermostatically opened solenoid valve?

It will move to a safe position if their is an electrical fault or power failure

How is the compressor protected from liquid passover

To prevent damage the liquid acts against the discharge valve causing the whole valve and valve body to lift against the spring tension allowing the liquid to escape

When would a DRIER be replaced

When a new change of oil has been put into the system

When oil analyst results indicate water content in an excess of 0.01%

When the refrigerant or lube oil systems have been open to the atmosphere

Why do we have back seated valves

To enable system isolation for changing and maintenance

What is the normal operating position of a back seated valve

Back seated, fully to the rear, fully open

Draw the refrigeration cycle and explain and explain what is happening to the refrigerant and explain all components

Compressor- a means of increasing the pressure so that the temperature ay which the vapor will condense if above cooling seawater

Condenser- gas gives up its latent health of condensation to the sea water and changes to liquid

Expansion valve- a means of reducing pressure so that the boiling point of the liquid is lower than required temperature of the coldest room

Evaporator- the liquid absorbs its heat of evaporation from the cooled food room and changes to gas

Why do we use a back pressure regulating valve on some systems

To maintain a different room temperature in a refrigerating system where more than one room is fed off the same compressor

What does the back pressure regulating valve do for our system

The lowest temperature that a room can come down too is directly related to the suction pressure in the evaporator. So by limiting the suction pressure we limit how cold the room can get

Label the back pressure regulating valve in the picture below